From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Testing twin S.U. carburettors and silencers on model 19.G.IV.
| Identifier | ExFiles\Box 13\4\ 04-page061 | |
| Date | 22th November 1932 | |
| To Hs{Lord Ernest Hives - Chair}/Rm.{William Robotham - Chief Engineer} From H.{Arthur M. Hanbury - Head Complaints} Whyman. TWIN S.U. CARBS. ON 19.G.IV. The first carburetters we tested were the H.V.5 type with inlet poet size of 1¾". This pair of carbs roar very badly, considerably worse than the R.R. semi-expanding carb. on P.II., and in our first effort to quieten them we fitted the largest type of air silencer that we had found so successful on P.II's. This had the effect of reducing the roar by about 50%. We next tried an American AC silencer, particulars of which are herewith attached. This silencer was not even as good as our first effort on this car and considering it loses about 7 BHP, at the higher speeds and weighs nearly 8 lbs. we hav'nt much use for it. With our silencer of course we used the same bore intake pipe, i.e., 2.587" that we had used on the P.II and as we already know a smaller bore has a considerable influence on Carb silence we are instructing for a pipe to be made with the bore 2.5", and we shall then continue our tests. Whilst waiting for this new part we tried a pair of S.U. carbs, designed I believe to Rm{William Robotham - Chief Engineer}'s specification of 1¾" inlet port, instead of the 1½" as on HV5 model and found them definitely 30% quieter. Performance Tests were taken on Ticknall Hill with both type of Carburetter as follows:- HV5 Type 1¾" Bore 62.4 secs. New Type 1¾" " 61.2 secs. Both these runs were taken on the same day i.e. 21.11.32. HS{Lord Ernest Hives - Chair}/H.Whyman. | ||